Explicit Proxy Request Is Forbidden
Error accessing site: Explicit proxy request forbidden – Google …
This post is a trending issue. Error accessing site: Explicit proxy request forbidden On my android devices I am getting “Error accessing site: Request denied. The explicit proxy request is is happening for many sites especially those which come up sponsored at the top of a google search, but also others. I have tried deleting cookies, history, cache etc. but no help appreciated. Thanks, Anna Latest Update Latest Updates (0) Recommended Answer Recommended Answers (3) Hi, I am Tarun, and I work on Data Saver in Chrome team. I’m sorry that you are having trouble browsing HTTP websites when data saver is enabled. We are looking at what might be causing this help us understand the cause, would it be possible for some of you to enable data saver back for a while, capture a log, and send them to my email address at are the steps to capture the logs:1. Enable data saver in chrome settings: For this, first on your Android phone or tablet, open the Chrome app. At the top right, tap More Settings. Under “Advanced, ” tap Data Saver. Turn on Data Saver. 2. Open a new Chrome browser window and browse to chromenet-export/3. Click Start logging to disk. This will start recording the network traffic. 5. In a different tab, open the website that you were having problem accessing. 6. Once you see the error “Explicit proxy request forbidden”, go back to the other tab where you were recording the network traffic. 7. Click on “Stop Logging”. 8. Click on “Email Log”. 9. Send it as an email attachment to for the help! Original Poster marked this as an answer Recommended based on info available Our automated system analyzes replies to choose the one that’s most likely to answer the question. If it seems to be helpful, we may eventually mark it as a Recommended Answer. Hi all, Thanks for posting in the Google Chrome community. I have escalated this issue to the Google Chrome team as a priority and have created a bug for it, which you can star to follow progress updates at In the meantime you should be able to workaround this by turning off the Data Saver feature: Original Poster marked this as an answer Recommended based on info available Our automated system analyzes replies to choose the one that’s most likely to answer the question. Hi all,
This issue is fixed in Chrome for Android 74. 0. 3729. 136 or higher. If you’re still experiencing an issue, please create a new topic for the community to best support you.
Original Poster marked this as an answer Recommended based on info available Our automated system analyzes replies to choose the one that’s most likely to answer the question. Relevant Answer Relevant Answers (0) Our automated system analyzes the replies to choose the one that’s most likely to answer the question. This question is locked and replying has been disabled. Failed to attach file, click here to try linkText to display:Link to: Notifications are currently off and you won’t receive updates. To turn them on, go to Notifications preferences on your Profile page. Discard post? You will lose what you have written so far. Personal information found We found the following personal information in your message: This information will be visible to anyone who visits or subscribes to notifications for this post. Are you sure you want to continue? This will remove the reply from the Answers section. Notifications are off Your notifications are currently off and you won’t receive subscription updates. To turn them on, go to Notifications preferences on your Profile page. Google user This reply is no longer available. Badges Some community members might have badges that indicate their identity or level of participation in a community.
Google Employee — Google product team members and community managers
Community Specialist — Google partners who help ensure the quality of community content
Diamond Product Expert — Community members with product mastery who help other Google users and Product Experts
Platinum Product Expert — Community members with advanced product knowledge who help other Google users and Product Experts
Gold Product Expert — Community members with in-depth product knowledge who help other Google users by answering questions
Silver Product Expert — Community members with intermediate product knowledge who help other Google users by answering questions
Product Expert Alumni — Former Product Experts who are no longer members of the program
Community content may not be verified or up-to-date.
Troubleshoot API Gateway 403 Forbidden errors – Amazon AWS
Last updated: 2021-05-19
When I call my Amazon API Gateway API, I get a 403 Forbidden error. How do I troubleshoot the error?
Short description
An HTTP 403 response code means that a client is forbidden from accessing a valid URL. The server understands the request, but it can’t fulfill the request because of client-side issues.
API Gateway APIs can return 403 Forbidden responses for any of the following reasons:
Issue
Response header
Error message
Details
Access denied
“x-amzn-ErrorType” = “AccessDeniedException”
“User is not authorized to access this resource with an explicit deny”
The caller isn’t authorized to access an API that’s using a Lambda authorizer.
“User:
The caller isn’t authorized to access an API that’s using AWS Identity and Access Management (IAM) authorization. Or, the API has an attached resource policy that explicitly denies access to the caller. For more information, see IAM authentication and resource policy.
“User: anonymous is not authorized to perform: execute-api:Invoke on resource:
The caller isn’t authorized to access an API that’s using IAM authorization. Or, the API has an attached resource policy that doesn’t explicitly allow the caller to invoke the API. For more information, see IAM authentication and resource policy.
“The security token included in the request is invalid. ”
The caller used invalid IAM keys to access an API that’s using IAM authorization.
Missing authentication token
“x-amzn-ErrorType” = “MissingAuthenticationTokenException”
“Missing Authentication Token”
An authentication token wasn’t found in the request.
Authentication token expired
“x-amzn-ErrorType” = “InvalidSignatureException”
“Signature expired”
The authentication token in the request has expired.
API key isn’t valid
“x-amzn-ErrorType” = “ForbiddenException”
“Invalid API Key identifier specified”
The caller used an invalid API key for a method that requires an API key.
Signature isn’t valid
“The request signature we calculated does not match the signature you provided. Check your AWS Secret Access Key and signing method. ”
The signature in the request doesn’t match that on the server when accessing an API that’s using IAM authorization.
AWS WAF filtered
“Forbidden”
The request is blocked by web application firewall (WAF) filtering when AWS WAF is activated in the API.
Resource path doesn’t exist
A request with no “Authorization” header is sent to an API resource path that doesn’t exist.
“x-amzn-ErrorType” = “IncompleteSignatureException”
“Authorization header requires ‘Credential’ parameter. Authorization header requires ‘Signature’ parameter. Authorization header requires ‘SignedHeaders’ parameter. Authorization header requires existence of either a ‘X-Amz-Date’ or a ‘Date’ header. Authorization=allow”
A request with an “Authorization” header is sent to an API resource path that doesn’t exist.
Invoking a private API using public DNS names incorrectly
When invoking a private API from within an Amazon Virtual Private Cloud (Amazon VPC) using public DNS names, the “Host” or “x-apigw-api-id” header is missing in the request. For more information, see Invoking your private API using endpoint-specific public DNS hostnames.
Invoking a REST API that has a custom domain name using the default execute-api endpoint.
The caller uses the default execute-api endpoint to invoke a REST API after disabling the default endpoint. For more information, see Disabling the default endpoint for a REST API.
Resolution
Follow these troubleshooting steps to help determine the cause of the error.
Consider the source of the error
If the 403 error was reported from other resources, there might be another cause for the error. For example:
If the error was reported in a web browser, then that error might be caused by an incorrect proxy setting. The proxy server returns a 403 error if HTTP access isn’t allowed.
If there’s another AWS service in front of the API (for example, Amazon CloudFront), then that service can reject the request with a 403 error in the response.
Set up API access logging to investigate.
Confirm that the requested resource exists in the API definition
Use curl to get request and response details
If the error can be reproduced, use curl -v to get more details between the client and the API.
curl -v command example
curl -X GET -v
If the error is about an API key, verify that the “x-api-key” header was sent in the request.
Check the DNS setting on a VPC endpoint
Check the resource policy
Verify the following:
If the API is invoked from an Amazon VPC with an interface VPC endpoint, the API’s resource policy must grant the Amazon VPC or the interface endpoint access to the API.
The resource policy’s resource specifications and formatting are correct. (There’s no validation of the resource specification when saving a resource policy. ) For examples, see API Gateway resource policy examples.
Analyze API access logs
Analyze HTTP request and response messages
If you can do so, reproduce the error in a web browser, and then use the browser’s network tools to capture the HTTP request and response messages for analysis. For offline analysis, save these messages in an HTTP Archive (HAR) file.
Note: For instructions on creating a HAR file, see How do I create a HAR file from my browser for an AWS Support case?
Then, analyze the requests and responses between the client and the API to determine where the error occurred.
Did this article help?
Do you need billing or technical support?
Proxy support in Chrome
This document establishes basic proxy terminology and describes Chrome-specific proxy server identifiersA proxy server is an intermediary used for network requests. A proxy server can be described by its address, along with the proxy scheme that should be used to communicate with can be written as a string using either the “PAC format” or the “URI format” PAC format is how one names a proxy server in Proxy auto-config scripts. For example:PROXY foo:2138SOCKS5 foo:1080DIRECTThe “URI format” instead encodes the information as a URL. For example:foo:2138foo:2138socks5foo:1080directThe port number is optional in both formats. When omitted, a per-scheme default is the Proxy server schemes section for details on what schemes Chrome supports, and how to write them in the PAC and URI UI surfaces in Chrome (including command lines and policy) expect URI formatted proxy server identifiers. However outside of Chrome, proxy servers are generally identified less precisely by just an address — the proxy scheme is assumed based on Windows’ proxy settings there are host and port fields for the “HTTP”, “Secure”, “FTP”, and “SOCKS” proxy. With the exception of “SOCKS”, those are all identifiers for insecure HTTP proxy servers (proxy scheme is assumed as HTTP) resolutionProxying in Chrome is done at the URL the browser is asked to fetch a URL, it needs to decide which IP endpoint to send the request to. This can be either a proxy server, or the target is called proxy resolution. The input to proxy resolution is a URL, and the output is an ordered list of proxy server proxies to use can be described using either:Manual proxy settings – proxy resolution is defined using a declarative set of rules. These rules are expressed as a mapping from URL scheme to proxy server identifier(s), and a list of proxy bypass rules for when to go DIRECT instead of using the mapped script – proxy resolution is defined using a JavaScript program, that is invoked whenever fetching a URL to get the list of proxy server identifiers to – the WPAD protocol is used to probe the network (using DHCP/DNS) and possibly discover the URL of a PAC server schemesWhen using an explicit proxy in the browser, multiple layers of the network request are impacted, depending on the scheme that is used. Some implications of the proxy scheme are:Is communication to the proxy done over a secure channel? Is name resolution (ex: DNS) done client side, or proxy side? What authentication schemes to the proxy server are supported? What network traffic can be sent through the proxy? Chrome supports these proxy server schemes:DIRECTHTTPHTTPSSOCKSv4SOCKSv5QUICDIRECT proxy schemeDefault port: N/A (neither host nor port are applicable)Example identifier (PAC): DIRECTExample identifier (URI): directThis is a pseudo proxy scheme that indicates instead of using a proxy we are sending the request directly to the target is imprecise to call this a “proxy server”, but it is a convenient proxy schemeDefault port: 80Example identifier (PAC): PROXY proxy:8080, proxy (non-standard; don’t use)Example identifiers (URI): proxy:8080, proxy:8080 (can omit scheme)Generally when one refers to a “proxy server” or “web proxy”, they are talking about an HTTP using an HTTP proxy in Chrome, name resolution is always deferred to the proxy. HTTP proxies can proxy,, ws and wss mmunication to HTTP proxy servers is insecure, meaning proxied requests are sent in the clear. When proxying requests through an HTTP proxy, the TLS exchange is forwarded through the proxy using the CONNECT method, so end-to-end encryption is not broken. However when establishing the tunnel, the hostname of the target URL is sent to the proxy server in the proxies in Chrome support the same HTTP authentiation schemes as for target servers: Basic, Digest, Negotiate, proxy schemeDefault port: 443Example identifier (PAC): HTTPS proxy:8080Example identifier (URI): proxy:8080This works like an HTTP proxy, except the communication to the proxy server is protected by TLS, and may negotiate HTTP/2 (but not QUIC). Because the connection to the proxy server is secure, requests sent through the proxy are not sent in the clear as with an HTTP proxy. Similarly, since CONNECT requests are sent over a protected channel, the hostnames for proxied URLs is also not addition to the usual HTTP authentication methods, HTTPS proxies also support client proxies using HTTP/2 can offer better performance in Chrome than a regular HTTP proxy due to higher connection limits (HTTP/1. 1 proxies in Chrome are limited to 32 simultaneous connections across all domains), Firefox, and Opera support HTTPS proxies; however, most older HTTP stacks do not. Specifying an HTTPS proxy is generally not possible through system proxy settings. Instead, one must use either a PAC script or a Chrome proxy setting (command line, extension, or policy) the document on secure web proxies for tips on how to run and test against an HTTPS CKSv4 proxy schemeDefault port: 1080Example identifiers (PAC): SOCKS4 proxy:8080, SOCKS proxy:8080Example identifier (URI): socks4proxy:8080SOCKSv4 is a simple transport layer proxy that wraps a TCP socket. Its use is transparent to the rest of the protocol stack; after an initial handshake when connecting the TCP socket (to the proxy), the rest of the loading stack is proxy authentication methods are supported for using a SOCKSv4 proxy, name resolution for target hosts is always done client side, and moreover must resolve to an IPv4 address (SOCKSv4 encodes target address as 4 octets, so IPv6 targets are not possible) are extensions to SOCKSv4 that allow for proxy side name resolution, and IPv6, namely SOCKSv4a. However Chrome does not allow configuring, or falling back to v4a. A better alternative is to just use the newer version of the protocol, SOCKSv5 (which is still 20+ years old). SOCKSv5 proxy schemeDefault port: 1080Example identifier (PAC): SOCKS5 proxy:8080Example identifiers (URI): socksproxy:8080, socks5proxy:8080SOCKSv5 is a transport layer proxy that wraps a TCP socket, and allows for name resolution to be deferred to the Chrome when a proxy’s scheme is set to SOCKSv5, name resolution is always done proxy side (even though the protocol allows for client side as well). In Firefox client side vs proxy side name resolution can be configured with; Chrome has no equivalent option and will always use proxy side authentication methods are supported for SOCKSv5 in Chrome (although some do exist for the protocol). A handy way to create a SOCKSv5 proxy is with ssh -D, which can be used to tunnel web traffic to a remote host over Chrome SOCKSv5 is only used to proxy TCP-based URL requests. It cannot be used to relay UDP proxy schemeDefault (UDP) port: 443Example identifier (PAC): QUIC proxy:8080Example identifier (URI): quicproxy:8080A QUIC proxy uses QUIC (UDP) as the underlying transport, but otherwise behaves as an HTTP proxy. It has similar properties to an HTTPS proxy, in that the connection to the proxy server is secure, and connection limits are less pport for QUIC proxies in Chrome is currently experimental and not ready for production use. In particular, sending and wss URLs through a QUIC proxy is disabled by default. Another caveat is that QUIC does not currently support client certificates since it does not use a TLS handshake. This may change in future proxy settingsThe simplest way to configure proxy resolution is by providing a static list of rules comprised of:A mapping of URL schemes to proxy server identifiers. A list of proxy bypass rulesWe refer to this mode of configuration as “manual proxy settings” proxy settings can succinctly describe setups like:Use proxy foo:8080 for all requestsUse proxy foo:8080 for all requests except those to a proxy foo:8080 for all requests, and proxy socsk5mysocks:90 for everything elseAlthough manual proxy settings are a ubiquituous way to configure proxies across platforms, there is no standard representation or feature ‘s manual proxy settings most closely resembles that of WinInet. But it also supports idioms from other platforms — for instance KDE’s notion of reversing the bypass list, or Gnome’s interpretation of bypass patterns as suffix defining manual proxy settings in Chrome, we specify three (possibly empty) lists of proxy server oxies for HTTP – A list of proxy server identifiers to use for requests, if oxies for HTTPS – A list of proxy server identifiers to use for requests, if proxies – A list of proxy server identifiers to use for everything else (whatever isn’t matched by the other two lists)There are a lot of ways to end up with manual proxy settings in Chrome (discussed in other sections) following examples will use the command line method. Launching Chrome with –proxy-server=XXX (and optionally –proxy-bypass-list=YYY)Example: To use proxy foo:8080 for all requests we can launch Chrome with –proxy-server=”foo:8080″. This translates to:proxies for HTTP – emptyproxies for HTTPS – emptyother proxies – foo:8080With the above configuration, if the proxy server was unreachable all requests would fail with ERR_PROXY_CONNECTION_FAILED. To address this we could add a fallback to DIRECT by launching using –proxy-server=”foo:8080, direct” (note the comma separated list). This command line means:proxies for HTTP – emptyproxies for HTTPS – emptyother proxies – foo:8080, directIf instead we wanted to proxy only URLs through the HTTPS proxy foo:443, and have everything else use the SOCKSv5 proxy socks5mysocks:1080 we could launch Chrome with –proxy-server=”=foo:443;socks=socks5mysocks:1080″. This now expands to:proxies for HTTP – foo:443proxies for HTTPS – emptyother proxies – socks5mysocks:1080The command line above uses WinInet’s proxy map format, with some additional features:Instead of naming proxy servers by just a hostname:port, you can use Chrome‘s URI format for proxy server identifiers. In other words, you can prefix the proxy scheme so it doesn’t default to socks= mapping is understood more broadly as “other proxies”. The subsequent proxy list can include proxies of any scheme, however if the scheme is omitted it will be understood as SOCKSv4 rather than pping WebSockets URLs to a proxyManual proxy settings don’t have mappings for ws or wss lecting a proxy for these URL schemes is a bit different from other URL schemes. The algorithm that Chrome uses is:If “other proxies” is non-empty use itIf “proxies for HTTPS” is non-empty use itOtherwise use “proxies for HTTP”This is per the recommendation in section 4. 1. 3 of RFC is possible to route ws and wss separately using a PAC credentials in manual proxy settingsMost platforms’ manual proxy settings allow specifying a cleartext username/password for proxy sign in. Chrome does not implement this, and will not use any credentials embedded in the proxy authentication will instead go through the ordinary flow to find bypass rulesIn addition to specifying three lists of proxy server identifiers, Chrome’s manual proxy settings lets you specify a list of “proxy bypass rules” ruleset determines whether a given URL should skip use of a proxy all together, even when a proxy is otherwise defined for concept is also known by names like “exception list”, “exclusion list” or “no proxy list” bypass rules can be written as an ordered list of strings. Ordering generally doesn’t matter, but may when using subtractive manual proxy settings are specified from the command line, the –proxy-bypass-list=”RULES” switch can be used, where RULES is a semicolon or comma separated list of bypass llowing are the string constructions for the bypass rules that Chrome supports. They can be used when defining a Chrome manual proxy settings from command line flags, extensions, or using system proxy settings, one should use the platform‘s rule format and not Chrome’ rule: Hostname[ URL_SCHEME “”] HOSTNAME_PATTERN [ “:”
Matches a hostname using a wildcard pattern, and an optional scheme and port – Matches URL of any scheme and port, whose normalized host is * – Matches URL of any scheme and port, whose normalized host ends with (for instance and). * – Matches URLs of any scheme, using port 443 and whose top level domain is – Matches URLs on port 99 whose normalized hostname matches x. *mBypass rule: Subdomain[ URL_SCHEME “”] “. ” HOSTNAME_SUFFIX_PATTERN [ “:” PORT]
Hostname patterns that start with a dot are special cased to mean a subdomain matches. is effectively another way of writing * – Matches and, but not – Matches only URLs that are a subdomain of rule: IP literal[ SCHEME “”] IP_LITERAL [ “:” PORT]
Matches URLs that are IP address literals, and optional scheme and port restrictions. This is a special case of hostname matching that takes into account IP literal canonicalization. For example the rules [0:0:0::1] and [::1] are equivalent (both represent the same IPv6 address). Examples:127. 0. 1::1] – Matches any URL to the IPv6 loopback address. [0:0::1] – Same as above[::1]:99 – Matches any URL to the IPv6 loopback on port 99Bypass rule: IPv4 address rangeIPV4_LITERAL “/” PREFIX_LENGTH_IN_BITS
Matches any URL whose hostname is an IPv4 literal, and falls between the given address this only applies to URLs that are IP literals. Examples:192. 168. 1/16Bypass rule: IPv6 address rangeIPV6_LITERAL “/” PREFIX_LENGTH_IN_BITS
Matches any URL that is an IPv6 literal that falls between the given range. Note that IPv6 literals must not be this only applies to URLs that are IP literals. Examples:fefe:13::abc/33[fefe::]/40 — WRONG! IPv6 literals must not be rule: Simple hostnames
Matches hostnames without a period in them, and that are not IP literals. This is a naive string search — meaning that periods appearing anywhere count (including trailing dots! ) rule corresponds to the “Exclude simple hostnames” checkbox on macOS and the “Don’t use proxy server for local (intranet) addresses” on rule name comes from WinInet, and can easily be confused with the concept of localhost. However the two concepts are completely orthogonal. In practice one wouldn’t add rules to bypass localhost, as it is already done rule: Subtract implicit rules<-loopback>
Subtracts the implicit proxy bypass rules (localhost and link local addresses). This is generally only needed for test setups. Beware of the security implications to proxying localhost. Whereas regular bypass rules instruct the browser about URLs that should not use the proxy, this rule has the opposite effect and tells the browser to instead use the proxy. Ordering may matter when using a subtractive rule, as rules will be evaluated in a left-to-right order. <-loopback>;127. 1 has a subtly different effect than 127. 1;<-loopback>. Meaning of IP address range bypass rulesThe IP address range bypass rules in manual proxy settings applies only to URL literals. This is not what one would intuitively expect. Example:Say we have have configured a proxy for all requests, but added a bypass rule for 192. 1/16. If we now navigate to foo (which resolves to 192. 5 in our setup) will the browser connect directly (bypass proxy) because we have indicated a bypass rule that includes this IP? It will go through the bypass rule in this case is not applicable, since the browser never actually does a name resolution for foo. Proxy resolution happens before name resolution, and depending on what proxy scheme is subsequently chosen, client side name resolution may never be usefulness of IP range proxy bypass rules is rather limited, as they only apply to requests whose URL was explicitly an IP proxy decisions need to be made based on the resolved IP address(es) of a URL’s hostname, one must use a PAC plicit bypass rulesRequests to certain hosts will not be sent through a proxy, and will instead be sent call these the implicit bypass rules. The implicit bypass rules match URLs whose host portion is either a localhost name or a link-local IP literal. Essentially it matches:localhost
*. localhost
[::1]
127. 1/8
169. 254/16
[FE80::]/10
The complete rules are slightly more complicated. For instance on Windows we will also recognize concept of implicit proxy bypass rules is consistent with the platform-level proxy support on Windows and macOS (albeit with some differences due to their implementation quirks – see compatibility notes in net::ProxyBypassRules::MatchesImplicitRules)Why apply implicit proxy bypass rules in the first place? Certainly there are considerations around ergonomics and user expectation, but the bigger problem is security. Since the web platform treats localhost as a secure origin, the ability to proxy it grants extra powers. This is especially problematic when proxy settings are externally controllable, as when using PAC scripts. Historical support in Chrome:Prior to M71 there were no implicit proxy bypass rules, except if using M71 Chrome applied implicit proxy bypass rules to PAC scriptsIn M72 Chrome generalized the implicit proxy bypass rules to manually configured proxiesOverriding the implicit bypass rulesIf you want traffic to localhost to be sent through a proxy despite the security concerns, it can be done by adding the special proxy bypass rule <-loopback>. This has the effect of subtracting the implicit instance, launch Chrome with the command line flag:–proxy-bypass-list=”<-loopback>”
Note that there currently is no mechanism to disable the implicit proxy bypass rules when using a PAC script. Proxy bypass lists only apply to manual settings, so the technique above cannot be used to let PAC scripts decide the proxy for localhost URLs. Evaluating proxy lists (proxy fallback)Proxy resolution results in a list of proxy server identifiers to use for a given request, not just a single proxy server instance, consider this PAC script:function FindProxyForURL(url, host) {
if (host == “) {
return “PROXY proxy1; HTTPS proxy2; SOCKS5 proxy3”;}
return “DIRECT”;}
What proxy will Chrome use for connections to, given that we have a choice of three separate proxy server identifiers to choose from {proxy1:80, proxy2:443, socks5proxy3:1080}? Initially, Chrome will try the proxies in order. This means first attempting the request through proxy1:80. If that “fails”, the request is next attempted through proxy2:443. Lastly if that fails, the request is attempted through socks5 process is referred to as proxy fallback. What constitutes a “failure” is described fallback is stateful. The actual order of proxy attempts made be Chrome is influenced by the past responsiveness of proxy ‘s say we request. Per the PAC script this resolves to a list of three proxy server identifiers:{proxy1:80, proxy2:443, socks5proxy3:1080}Chrome will first attempt to issue the request through these proxies in the left-to-right ‘s say that the attempt through proxy1:80 fails, but then the attempt through proxy2:443 succeeds. Chrome will mark proxy1:80 as bad for the next 5 minutes. Being marked as bad means that proxy1:80 is de-prioritized with respect to other proxy server identifiers (including direct) that are not marked as means the next time is requested, the effective order for proxies to attempt will be:{proxy2:443, socks5proxy3:1080, proxy1:80}Conceptually, bad proxies are moved to the end of the list, rather than being removed from consideration all constitutes a “failure” when it comes to triggering proxy fallback depends on the proxy type. Generally speaking, only connection level failures are deemed eligible for proxy fallback. This includes:Failure resolving the proxy server’s DNSFailure connecting a TCP socket to the proxy server(There are some caveats for how HTTPS and QUIC proxies count failures for fallback)Prior to M67, Chrome would consider failures establishing a CONNECT tunnel as an error eligible for proxy fallback. This policy resulted in problems for deployments whose HTTP proxies intentionally failed certain requests, since that necessitates inducing a failure during the CONNECT tunnel establishment. The problem would occur when a working proxy fallback option like DIRECT was given, since the failing proxy would then be marked as rrently there are no options to configure proxy fallback (including disabling the caching of bad proxies). Future versions of Chrome may remove caching of bad proxies to make fallback investigate issues relating to proxy fallback, one can collect a NetLog dump using chromenet-export/. These logs can then be loaded with the NetLog are a few things of interest in the logs:The “Proxy” tab will show which proxies (if any) were marked as bad at the time the capture “Events” tab notes what the resolved proxy list was, and what the re-ordered proxy list was after taking into account bad “Events” tab notes when a proxy is marked as bad and why (provided the event occurred while capturing was enabled) debugging issues with bad proxies, it is also useful to reset Chrome’s cache of bad proxies. This can be done by clicking the “Clear bad proxies” button on chromenet-internals/#proxy. Note the UI will not give feedback that the bad proxies were cleared, however capturing a new NetLog dump can confirm it was guments passed to FindProxyForURL() in PAC scriptsPAC scripts in Chrome are expected to define a JavaScript function historical signature for this function is:function FindProxyForURL(url, host) {… }
Scripts can expect to be called with string arguments url and host such that:url is a sanitized version of the request’s URLhost is the unbracketed host portion of the nitization of the URL means that the path, query, fragment, and identity portions of the URL are stripped. Effectively url will be limited to a schemehost:port/ style URLExamples of how FindProxyForURL() will be called Actual URL: FindProxyForURL(”, ”)
// Actual URL: [dead::beef]/foo? bar
FindProxyForURL(‘[dead::beef]/’, ‘dead::beef’)
// Actual URL: FindProxyForURL(”, ”)
// Actual URL: username:password@FindProxyForURL(”, ”)
Stripping the path and query from the url is a departure from the original Netscape implementation of PAC. It was introduced in Chrome 52 for security is currently no option to turn off sanitization of URLs passed to PAC scripts (removed in Chrome 75) sanitization of URLs currently has a different policy, and does not strip query and path portions of the URL. That said, users are advised not to depend on reading the query/path portion of any URL type, since future versions of Chrome may deprecate that capability in favor of a consistent solving client’s IP address within a PAC script using myIpAddress()PAC scripts can invoke myIpAddress() to obtain the client’s IP address. This function returns a single IP literal, or “127. 1” on API is inherently ambiguous when used on multi-homed hosts, as such hosts can have multiple IP addresses and yet the browser can pick just one to ‘s algorithm for myIpAddress() favors returning the IP that would be used if we were to connect to the public internet, by executing the following ordered steps and short-circuiting once the first candidate IP is found:Select the IP of an interface that can route to public Internet:Probe for route to for route to an IP by doing a DNS resolve of the machine’s hostname:Select the first IPv4 result if there is the first IP result if there is the IP of an interface that can route to private IP space:Probe for route to for route to for route to for route to that when searching for candidate IP addresses, link-local and loopback addresses are skipped over. Link-local or loopback address will only be returned as a last resort when no other IP address was found by following these sequence of steps explicitly favors IPv4 over IPv6 results, to match Internet Explorer’s IPv6 support. Historical note: Prior to M72, Chrome’s implementation of myIpAddress() was effectively just getaddrinfo(gethostname). This is now step 2 of the solving client’s IP address within a PAC script using myIpAddressEx()Chrome supports the Microsoft PAC extension myIpAddressEx() is like myIpAddress(), but instead of returning a single IP address, it can return multiple IP addresses. It returns a string containing a semi-colon separated list of addresses. On failure it returns an empty string to indicate no results (whereas myIpAddress() returns 127. 1) are some differences with Chrome’s implementation:In Chrome the function is unconditionally defined, whereas in Internet Explorer one must have used the FindProxyForURLEx does not necessarily enumerate all of the host’s network interfacesChrome does not return link-local or loopback addresses (except if no other addresses were found) algorithm that Chrome uses is nearly identical to that of myIpAddress() described earlier, but in certain cases may return multiple all the IPs of interfaces that can route to public Internet:Probe for route to for route to any IPs were found, return them, and an IP by doing a DNS resolve of the machine’s hostname:If any IPs were found, return them, and the IP of an interface that can route to private IP space:Probe for route to for route to for route to for route to any IPs were found, return them, and that short-circuiting happens whenever steps 1-3 find a candidate IP. So for example if at least one IP address was discovered by checking routes to public Internet, only those IPs will be returned, and steps 2-3 will not IpAddress() / myIpAddressEx() and multi-homed hostsmyIpAddress() is a poor API for hosts that have multiple IP addresses, as it can only return a single IP, which may or may not be the one you wanted. Both myIpAddress() and myIpAddressEx() favor returning the IP for the interface that would be used to route to the public an API, myIpAddressEx() offers more flexibility since it can return multiple IP addresses. However Chrome‘s implementation restricts which IPs a PAC script can see due to privacy concerns. So using myIpAddressEx() is not as powerful as enumerating all the host’s IPs, and may not address all use-cases. A more reliable strategy for PAC scripts to check which network(s) a user is on is to probe test domains using dnsResolve() / dnsResolveEx(). Moreover, note that Chrome does not support the Firefox-specific pacUseMultihomedDNS option, so adding that global to a PAC script has no special side-effect in Chrome. Whereas in Firefox it reconfigures myIpAddress() to be dependent on the target URL that FindProxyForURL() was called quirksProxy resolving via PAC works differently on Android than other desktop Chrome platforms:Android Chrome uses the same Chromium PAC resolver, however does not run it out-of-process as on Desktop Chrome. This architectural difference is due to the higher process cost on Android, and means Android Chrome is more susceptible to malicious PAC scripts. The other consequence is that Android Chrome can have distinct regressions from Desktop Chrome as the service setup is quite different (and most browser_tests are not run on Android either). WebView does not use Chrome’s PAC resolver. Instead Android WebView uses the Android system‘s PAC resolver, which is less optimized and uses an old build of V8. When the system is configured to use PAC, Android WebView’s net code will see the proxy settings as being a single HTTP proxy on localhost. The system localhost proxy will in turn evaluate the PAC script and forward the HTTP request on to the resolved proxy. This translation has a number of effects, including what proxy schemes are supported, the maximum connection limits, how proxy fallback works, and overall performance (the current Android PAC evaluator blocks on DNS). Android system log messages for PacProcessor are not related to Chrome or its PAC evaluator. Rather, these are log messages generated by the Android system’s PAC implementation. This confusion can arise when users add alert() to debug PAC script logic, and then refer to output in logcat to try and diagnose a resolving issue in Android wnloading PAC scriptsWhen a network context is configured to use a PAC script, proxy resolution will stall while downloading the PAC script. Fetches for PAC URLs are initiated by the network stack, and behave differently from ordinary web visible requests:Must complete within 30 complete with an HTTP response code of exactly have an uncompressed body smaller than 1 not follow ordinary HTTP caching never fetched through a proxyAre not visible to the WebRequest extension API, or to service not support HTTP authentication (ambient authentication may work, but cannot prompt UI for credentials) not support client certificates (including AutoSelectCertificateForUrls)Do not support auxiliary certificate network fetches (will only used cached OCSP, AIA, and CRL responses during certificate verification). Caching of successful PAC fetchesPAC URLs are always fetched from the network, and never from the HTTP cache. After a PAC URL is successfully fetched, its contents (which are used to create a long-lived Java Script context) will be assumed to be fresh until either:The network changes (IP address changes, DNS configuration changes)The response becomes older than 12 hoursA user explicitly invalidates PAC through chromenet-internals#proxyOnce considered stale, the PAC URL will be re-fetched the next time proxy resolution is requested. Fallback for failed PAC fetchesWhen the proxy settings are configured to use a PAC URL, and that PAC URL cannot be fetched, proxy resolution will fallback to the next option, which is often DIRECT:If using system proxy settings, and the platform supports fallback to manual proxy settings (e. g. Windows), the specified manual proxy servers will be used after the PAC fetch using Chrome’s proxy settings, and the PAC script was marked as mandatory, fallback to DIRECT is not permitted. Subsequent network requests will fail proxy resolution and complete with ERR_MANDATORY_PROXY_CONFIGURATION_FAILED. Otherwise proxy resolution will silently fall back to covering from failed PAC fetchesWhen fetching an explicitly configured PAC URL fails, the browser will try to re-fetch it:In exactly 8 seconds32 seconds after that2 minutes after thatEvery 4 hours thereafterThis background polling of the PAC URL is only initiated in response to an incoming proxy resolution request, so it will not trigger work when the browser is otherwise milarly to successful fetches, the PAC URL will be also be re-fetched whenever the network changes, the proxy settings change, or it was manually invalidated via chrome encodingNote that UTF-8 is not the default interpretation of PAC response priority for encoding is determined in this order:The charset property of the HTTP response’s Content-TypeAny BOM at the start of response bodyOtherwise defaults to setting the Content-Type, servers should prefer using a mime type of application/x-ns-proxy-autoconfig or application/x-javascript-config. However in practice, Chrome does not enforce the mime pturing a Net Log for debugging proxy resolution issuesIssues in proxy resolution are best investigated using a Net Log. A good starting point is to follow the general instructions for net-export, and while the Net Log is being captured perform these steps:Reproduce the failure (ex: load a URL that fails)If you can reproduce a success, do so (ex: load a different URL that succeeds) a new tab, navigate to chromenet-internals/#proxy and click both buttons (“Re-apply settings” and “Clear bad proxies”) step (1)Stop the Net Log and save the resulting Net Log should have enough information to diagnose common problems. It can be attached to a bug report, or explored using the Net Log Viewer. See the next section for some tips on analyzing it. Analyzing Net Logs for proxy issuesLoad saved Net Logs using Net Log overview tabStart by getting a big-picture view of the proxy settings by clicking to the “Proxy” tab on the left. This summarizes the proxy settings at the time the capture the original proxy settings match expectation? The proxy settings might be coming from:Managed Chrome policy (chromepolicy)Command line flags (ex: –proxy-server)(per-profile) Chrome extensions (ex:)(per-network) System proxy settingsWas proxy autodetect (WPAD) specified? In this case the final URL probed will be reflected by the difference between the “Effective” and “Original” ternally, proxy settings are per-NetworkContext. The proxy overview tab shows settings for a particular NetworkContext, namely the one associated with the Profile used to navigate to chromenet-export. For instance if the net-export was initiated from an Incognito window, it may show different proxy settings here than a net-export capture initiated by a non-Incognito window. When the net-export was triggered from command line (–log-net-log) no particular NetworkContext is associated with the capture and hence no pr
Frequently Asked Questions about explicit proxy request is forbidden
How do I fix my proxy server on Google Chrome?
If you see the message “Resolving proxy” or “ERR_PROXY_CONNECTION_FAILED” in your browser window, you can change your proxy settings.At the bottom right, select the time.Select Settings .In the “Network” section, select the network you’re using.Select the network name again.Select Proxy.Change your proxy settings.
How do I fix error 403 in Chrome?
Reset everything: If the 403 forbidden error on Google Chrome only happens on a specific internet connection, turn off your router or modem, wait a few seconds and then turn things back on again. Hopefully by rebooting your connection the issue will solve itself.Jun 18, 2021
How do I disable proxy settings in Chrome?
Disable proxy for Chrome on WindowsClick the Chrome Menu in the browser toolbar.Select Settings.Click Advanced.In the System section, click Open your computer’s proxy settings. … Under Automatic proxy setup, toggle Automatic detect settings Off.Under Manual proxy setup, toggle Use a proxy server Off.Click Save.Aug 12, 2021
